DOC: Bring the PMP page up to date with the service

[jwrosewell]

The two faults reported

Both were found working on the 51Degrees website against cloud release
4.4.38.

The script tag on the PMP page does not work. The page showed

https://cloud.51degrees.com/api/v4/pmp?resource=YOUR-RESOURCE-KEY

and that address answers 404, so anyone copying the tag off the page
fetched nothing and saw no dialog. The resource key goes in the path now,
which is the shape every other keyed request takes:

https://cloud.51degrees.com/api/v4/pmp/YOUR-RESOURCE-KEY.js

data-resource-key on the tag is not read either, so the key has one home
and a page cannot carry one the cloud never sees.

The alternative button does not store standard. It stores
non-marketing, which is the visitor declining marketing. The change was
made so that a publisher reading an answer shared from another site can
tell a visitor who declined from one who accepted the lesser of the two
kinds. The page still said standard, and it also said that visitors
taking that path avoid personalized advertising but are still covered by
standard marketing tracking, which is the opposite of what happens now.

What else on the page was out of date

Having found two, I checked the rest of the page against the service
rather than fixing only the two, and rewrote the page where it no longer
matched:

• The endpoints. A page view now makes two requests, the loader and
  the bundle the loader decides is needed. The page described one. Which
  of the two is checked and counted is worth knowing, as is the fact that
  the resource key has to be registered for the domain the page is on and
  a page suppressing the Referer header is refused.
• Where the language comes from. The page said the locale is picked
  from an accept-language query parameter or the Accept-Language
  header. The loader picks it from the visitor's own browser.
• The 51Degrees client script. It was not mentioned at all, and PMP
  reads two things from it, being whether third party cookies work in
  this browser and whether the General Data Protection Regulation
  applies. The page now says to put it on the page, that either order
  works with async on both, and what PMP does where no object appears.
• The configuration table. It claimed to be the full set and was
  missing data-license-key, data-network-name, data-network-logo,
  data-use-third-party-cookies and data-object-name. It also marked
  data-action-url as required, which it is not. data-timeout is no
  longer read and a page that still sets it gets a console warning, so
  that is now said too.
• What the action URL is for. The page had it as the continuation
  that fetches the 51Did, with the client script address and
  id.usage={preference} on it. That loaded the client script again on
  every answer. The client script hears the answer on the window and
  sends it as id.usage itself, so the action URL is a hook for a
  publisher's own code, and one naming the cloud is skipped with a
  console message.
• The id.usage mapping. non-marketing was missing from the table
  of three values. What a resource key without the 51Did product does and
  does not still do is now said, since the question is asked either way
  and only the answer's result changes.
• Sharing an answer across sites. The second card was not described
  at all, nor the three things that have to hold before it is offered.
• The dialog. The first card has no close cross, and after an answer
  it collapses to a bubble that reopens it, which is how a visitor
  changes an answer without clearing storage. The page only described
  clearing the localStorage key.
• The browser requirement. ES2020, which matters most for
  televisions, set-top boxes and games consoles.

The localStorage key and shape are unchanged, apart from p now
carrying one of three values rather than two.

Two other pages carried the same faults

• src/identifiers/overview.md expanded PMP as "Privacy Marketing
  Preference". It is the Preference Management Platform. The same line
  listed two preference values where there are three.
• src/identifiers/fodid.md said PMP "fires the request with id.usage
  already set". PMP announces the answer on the page and the 51Degrees
  client script hears it and sends it.

Checked and not changed

• src/devicedetection/otherintegrations/wordpress.md describes the
  WordPress plugin's PMP tab and says the choice needs "no cookies and no
  extra server round-trips". Whether that still holds depends on how the
  plugin configures the tag, which is not something this repository can
  answer, so I have left it and raised it separately.
• The purposes PMP encodes into its TCF consent string and the purposes
  the cloud requires when it derives id.usage from a TCF string are not
  the same sets. The derivation is only used by callers who hand the
  cloud a raw string, and PMP sends id.usage directly, so nothing on
  these pages is wrong because of it. I have left the two alone rather
  than writing a reconciliation I cannot stand behind, and it is worth
  someone who owns both checking.

Evidence

Every statement added or changed was checked against the service's own
source and its tests, not against prose about it. The 404 on the old
address is pinned by an integration test gated to release 4.4.38.

This repository's .utm-lint.json is { "mode": "forbid" }, so no
campaign tags were added to any link. scripts/utm-lint.ps1 from
common-ci run against the working tree reports UTM link lint: clean.

The Preview Documentation workflow does run on a pull request, and it ran
on this branch's current head, d26e57e, run
35169124239,
and succeeded. Its log shows src/identifiers/pmp.md,
src/identifiers/overview.md and src/identifiers/fodid.md all read and
Generating docs for page Identifiers_PMP, so the three changed pages were
rendered. The warnings in that log are the Doxyfile and tag file ones the
build already carried. The UTM link lint passed as well, run
35169124212.
The markup uses only @page and @ref, which the page already used, and
every @ref target on it resolves to a page in this repository.

main here requires one approving review, so nothing merges this on its
own and a person has to approve it first.

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